Create a company in your school. Only name is required, and names are not unique: two companies may share one. Unknown fields are refused. Creating a company attaches nobody to it.

Idempotency: send your own externalReferenceId (with externalReferenceType). It is unique within your school, so a retried creation answers 409 COMPANY_ALREADY_EXISTS instead of creating a duplicate: find the company with POST /companies:search (filters.externalReferenceIds) and update it with PATCH /companies/by-reference-id/{externalReferenceId}. businessIdentifier is unique within your school as well (409 COMPANY_BUSINESS_IDENTIFIER_ALREADY_EXISTS). Without either, two identical requests create two companies.

Several learners and external contacts can be attached to one company, and a change to the company applies to all of them.

Attach a learner with companyId on PATCH /students/{id} (or its by-reference-id twin): it is the "Company" field of the learner record in the School app. That call also copies the company display name into the learner's historical company text; updating the company later does not rewrite that text.